You need to have a full day. People who have an active day are more likely to conk out earlier and have longer periods of restful sleep at night. Some exercise during the day is a good substitute for a busy day.
Don’t look at the clock! Turn it around. Put it in a drawer. You can’t possibly relax if you watch the minutes ticking away and you’re calculating how many hours of sleep you have left before you have to get up.
Get up and relax. If you can’t sleep, don’t just toss and turn. Get up and do something relaxing. What sometimes happens to me is I get more and more tired as my usual time to sleep approaches, but if I keep myself up past that time, I get less and less tired until I’m wide awake. What helps then is I take a difficult book, maybe philosophy, and start reading it. I’m so awake that it seems easy to read. That lasts about 20 minutes and then I’m tired out. But now my mind is full of deep thoughts and it feels satisfied. That helps me sleep. Maybe watching some TV will do it for you, or reading something boring, like a technical manual for building a swing set.
Also, have some warm tea. Then build that swing set.